Know Thy Enemy
by Yuna Yami Mouto
Summary: I just rewatched S1 and part of S2 of TFP and wondered how else episode Nemesis Prime could have gone if a certain warlord got involved. Two different ways it could have gone. Mech on mech slash.
1. Chapter 1

**Know Thy Enemy**

**Summary: I just rewatched S1 and part of S2 of TFP and wondered how else episode Nemesis Prime could have gone if a certain warlord got involved. Two different ways it could have gone. Mech on mech slash.**

The second Bumblebee didn't give in his regular time report back to Ratchet, the medic had given the rest of the team his last coordinates and they immediately started driving towards the scout's last known location. But even beneath the almost tangible worry he felt for Bumblebee's wellbeing, the practical and strategic thinking part of Optimus Prime rebelled at the idea of putting any more of his soldiers, his friends, his _family_ in reach of MECH's dangerous hands while his sinister double roamed the streets. Agent Fowler had already nearly perished at the hands of Nemesis Prime, as Miko insisted on calling him, and even the ever careful Arcee had been run off. Optimus won't have any more of his friends suffer at MECH's malicious servo, so he ordered Arcee and Bulkhead to fall back. He ignored their protests even as he stayed his course towards Bumblebee.

"So far, I am the only one they have not encountered up close and I have the best chances of getting out of this without critical damage. I will _not_ allow any of you to be taken and experimented on, as has been the case so far. MECH is ready to tear us apart for their own schemes and I will not risk any of your lives. None of you have fought me before. It is far too dangerous for any of you to engage my double."

They had tried protesting further, that they stood a better chance as a united front, but Optimus wasn't having any of it. MECH has hurt them before. Bulkhead could have ended up in Breakdown's place, almost dissected and loosing an optic. Arcee was almost taken apart for parts as well. Bumblebee had actually had his T-Cog stolen from him. He was their leader and he refused to have some knockoff copy of him threaten their lives when they were already under enough threat from the war with the Decepticons that he was not strong enough to end.

"No offense, Optimus, but neither have you," Arcee had stated, worry clear in her voice even over the comm link. His team had never quite stopped worrying about him since his episode of amnesia and spending weeks with the Decepticons as Orion Pax. Optimus tried not to think about what Ratchet might have told them. His and Megatron's past as Orion Pax and Megatronus was their business and he would have appreciated it if Ratchet hadn't gone sharing it with others without his permission or so much as an apology after his return. Those were old wounds that had never managed to heal, no matter how much time had past. They only grew deeper every time Megatron showed just how much he had strayed from their original path.

"Arcee _is_ right, Optimus," Ratchet had agreed, sounding apologetic. "You've never fought yourself. You may know how to _protect_ your weak spots, but you don't know how to take advantage of them."

"No," he had admitted even as he searched for a frequency he had not hailed in millions of years. He could only hope it was still in use. "But I do know someone who does."

He muted the link before any of them could react and sent a single, simple message and a set of coordinates.

For once, he hoped the other was up for a fight.

00000

Megatron wasn't sure what he had been expecting of his night, but receiving a message from a comm frequency that has been blocked to him from the day he stormed out of the Council Chamber was not what he had thought might happen to him. He wondered what his dearest enemy might want now, even for a moment entertained the idea that whatever his underlings and that infernal human had done with the Matrix had worn off and poor, scared little Orion Pax was calling on Megatronus again because he was scared of the unknown mecha around him, but the message he got reminded him a bit too much of the day _before_ he got his little archivist back, even if only for a short while.

_::It is time we settle this once and for all. Come to these coordinates. Come alone.::_ That was it. That little message and a set of coordinates in relative proximity to where he had shot Bumblebee's human pet in the days preceding the awakening of Unicron. Megatron wondered what Optimus' angle might be. He _could_ be trying to trick him into a trap and use the Spark Extractor on him, but he had insisted on him coming alone, when bringing a troop of soldiers would better help the Autobots as it meant less soldiers for his mechs to fight. Besides, Optimus was too kind to use such a weapon on any mech, even those who deserved it the most. So it would seem Optimus wanted a rematch from last time.

_'Or revenge, for what I did to Orion Pax,'_ he pondered even as he approached the dark human facility. It looked abandoned and spacious enough for a good brawl. Still not quite like Optimus to choose something so close to the local species' populated places, but who was he to care about little fleshlings? If Optimus wanted to fight here, he had no qualms about it.

He transformed to root mode in the air and landed heavily on his pedes a second later, making the ground tremble from his weight. He smirked, thinking back to days when he used his size and such dramatic entrances in the gladiatorial arena to intimidate his opponents who were already halfway to leaking themselves at the prospect of facing against the Champion of the Pits of Kaon. In fact, the only mechs who had never cowered before him were Soundwave, the previous champion until Megatronus came along, and none other than a little, shiny, Iaconian archivist with nothing but his words and a datapad as his defense against a mech he had only moments ago seen tear apart an Insecticon. He knew no entrance he made will frighten Optimus but he'd be a liar if he said he didn't have a flair for the dramatics. Not to mention that such entrances always ensured him all of Optimus' attention, no matter what else was going on around them. He loved how those oh so blue optics scanned him, even if it was just Optimus readying himself for an attack and it no longer held the awed admiration of a mech he used to be able to pick up with a single servo.

He frowned when he didn't immediately see Optimus anywhere around him and frowned further when there was no sign of an EM field close by. _'Perhaps his lapdog of a medic has managed to invent some sort of signal dampener to give him the element of surprise.'_ He most often than not regretted the loss of Shockwave. He was loyal and competent and quite possibly the greatest processor Cybertron has produced since the time of the original Primes, if they had even existed at all. He would have been greatly useful if he had not offlined in that explosion Starscream had barely survived. If Megatron could choose, he would have chosen for Shockwave to survive. But it was all in the past now. He could not waste time on old memories if he knows he has an opponent here but cannot sense their approach. Optimus was quite good at sneaking around when he wants to. He needs to put his senses to their maximum if he wants to see the first attack before it lands. Failure to do so might cost him his life. _Especially_ if Optimus was here for revenge about what had been done to him as Orion. It would be unusual for the oh so noble Prime, yes, but even _he_ had to have his limits.

Megatron still remembered the cold fury in his optics when they had fought at the base of Unicron's volcano and it made his plating shudder tightly against his protoform. Even before he had spoken to the Chaos Bringer, that image had screamed at him "angered god" and for the first time in his entire function, he had felt a cold, strut-deep fear. That had not been the Optimus he knew, nor Orion Pax. For just that one moment, he had stared a true _Prime_ in the optics, a mech powerful enough to bear the Matrix of Leadership in his spark and survive dispersing its power into Unicron's dark spark. If Optimus had been ready to kill him once before, what was to stop him from doing so again?

With his senses on high alert, he walked for not a minute before he registered a presence in the shadows and he whirled around. There, between the two big constructs that Megatron didn't really care what they were for, stood the all too familiar form of his oldest enemy. Broad shoulder, narrow waist, long, shapely legs and a helm with those adorable finials and the high, proud forehead crest. He could be blind and he would recognize the form of Optimus Prime. "Optimus! And here I thought you backed out at the last minute."

The mech before him turned around, something ... not quite right in his movement. In fact, he held himself all wrong. Even as a data archivist, Orion had held himself more regally than that fake Prime, Sentinel, ever could. The shape of the body in front of him was right, but the motions were all wrong. Yes, Optimus had always held himself as a fighter: proud back straight, shoulders bravely squared, helm held high as he regarded any enemy that might oppose him, be it verbally or physically. But that wasn't everything. Whether he knew it or not, both as Orion Pax and as Optimus Prime, he had a very _sensual_ motion to his hips, whether he was standing still, charging into battle or strolling into a verbal sparring match. It could be quite distracting, if one was not used to it or of a weak processor and resolve. Gladiators and soldiers both had ran into things when the red and blue mech used to pass them by on his way to Megatron, whether it be in the streets of Kaon or the battlefield. The shape before him was right and held itself halfway decently, but it lacked that sensual presence his nemesis always possessed. And not only that.

Seen or unseen, heard or unheard, Optimus Prime's presence was _always_ felt. It wasn't even just Megatron. Every bot felt it when Optimus Prime set foot on the battlefield. The Autobots started fighting harder, the Decepticons found it far more difficult to hold the line but they didn't give up ground easily, either, though most of their fields sang with the need to _run_ and Megatron always felt his spark skip a few harmonics. Optimus could be on the other side of the battlefield entirely, miles upon miles separating them so not even their sharp optics could pick each other up and yet he'd _always_ know Optimus was there.

This form before him garnered no such reaction. Megatron sneered, mind whirling back to the state Breakdown returned in from his capture by the disgusting humans, putting some of the pieces of the puzzle together before he even caught sight of the other's optics. Wrong. They were all _wrong_. Even though the light of the full moon distorted the colors around them, Optimus' optics should have been blazing that same captivating color that Megatron was used to, that Megatronus had been drawn into the first time he set his sight on the data clerk.

"Who are you and what have you done to the _real_ Optimus Prime?"

00000

Optimus' plating gave an involuntary rattle as it shivered at hearing that growl. He knew it well and his spark gave a painful thud against the Matrix, calling out to the one that always excited it so. It has been millennia since the last time he had heard Megatron emit that growl. Protective, possessive and promising unspeakable bodily harm and unthinkable property damage if the location of his archivist brother was not revealed to him immediately. As far as he knew, the only one to never be on the receiving end of that growl was Soundwave himself, Megatronus' oldest and most trusted friend and ally.

"I had to be blindsided by that thing and to see it standing opposite Optimus to realize the difference and he takes one look and immediately recognizes it as a fake?!" The incredulous Arcee obviously can't help but exclaim in shock and Optimus' winces at her tone. She was probably embarrassed already for sounding so shrill in the first place, so he makes no comment.

"Optimus, do you see Bumblebee?" Ratchet, thankfully, doesn't comment and instead focuses on the important things. Optimus, making sure to keep his field held as tightly to his frame as he can manage while sneaking around as silently as a mechanism his size can, kept a wary optic on the two bots facing each other as he searches for his young scout. If he is lucky and his plan works, Megatron will take care of MECH while he'll manage to find Bumblebee and get him through a ground bridge unnoticed.

"Negative, old friend, but prepare a ground bridge none the less. He cannot be far."

"What's going on out there?" He hears Bulkhead inquire and he activates a link to the base's computers so they have a visual of what he sees. They all sigh in relief when he spots something yellow not too far away, but they also all wince when the clang of metal hitting metal echoes in the silence of the night. He doesn't answer except to tell Ratchet to open a bridge and to get Bumblebee through before he focuses his whole attention on what's going on in front of him.

00000

"I must admit, I'm impressed. It took the other robots a lot longer to figure that out," the imposter said in sub-vocals that were distinctly human despite the robotic drawl of the vocalizer it was using. Megatron growled, optics narrowed, EM field lashing out in anger. The other didn't react, only straightening Megatron's suspicions about this _fake _being a drone. Created by the fleshlings of this pathetic, cursed planet, no doubt. "You're a new one, though. I've never seen you before."

"I have no patience for the likes of you," Megatron grit out between tightly clenched denta, glare like blazing red fire that would send any smart being running for their lives. "I will _not _ask again. Who are you and what have you done with the real Optimus Prime?"

"I am Silas, but more importantly, we are MECH," 'Silas' responded in a proud, arrogant tone that reminded Megatron of the enforcers back on Cybertron who thought they could abuse their meager power over the lower caste mechs until Megatron had ripped a corrupt cop apart in Kaon when he tried to force himself on a starving femmeling in the middle of the streets. It only made him hate the human and the impersonator of his rival even _more_. "I was honestly expecting Optimus Prime here, but instead I got you. And just who might _you _be?"

"Megatron of Kaon, the Lord of the Decepticons. Why are you impersonating Optimus Prime, filth?"

"Oh, so you're the leader of the faction Arachnid abandoned?" Megatron felt sickened at the interest in the other's vocals. "I wondered what kind of person would have someone like her fearing for her life and ensuring she behaves. You're obviously intelligent and observant and you look like you pack quite a bit of power in that body of yours. You'd make a good soldier for us. Just how could you tell so easily that I'm not the real thing?" The fake stepped into the light of the moon, revealing the almost brown paint and the yellow optics. "The other robots couldn't."

"Answer my question, human, or else you will not like the consequences when I lose my patience." The warlord growled low in his chest and the sound vibrated through the silent, cool, night air like a physical threat.

"MECH is always searching for new technology. As soon as we learned of your species' presence on Earth, we started studying you until we finally managed to build you. Optimus Prime was the strongest, sturdiest robot we knew of, so we made a copy of him. Only we made him _better_."

Megatron couldn't help it. He laughed in the human's face. The mere notion of someone thinking they could create a better Optimus Prime than the bot himself was so ridiculous it was bordering on mad. "You are so delusional, human, that I actually pity you. You can't make a _better _Optimus Prime!"

"And why is that?" Ah, he had managed to annoy the human. Good. Now he knew how Megatron felt. He had come out here because Optimu had sent him a message, but instead of finding the Prime, he found this ... weak _copy _in front of him that couldn't stand up to Optimus on his deathbed.

"Because Optimus Prime is perfect," replied the gray mech instantly, feeling no shame in admitting something that he had thought even before the Matrix had reformatted his enemy. "From spark to mind to frame, Optimus Prime is the pinnacle of perfection in a Cybertronian. A little too naively idealistic and optimistic, perhaps, but even Primes aren't flawless." He grinned nastily at the fake, showing off his sharp dentae. "What made it so easy to tell you apart from the real Optimus Prime is that you've chosen to replicate the closest thing to perfection itself and you've failed miserably."

"I find myself doubting your words, Megatron of Kaon, as I am quite confident this perfect mend of man and machine can defeat you." Megatron only grinned more at that. A fight is what he had been invited to, so a fight is what he will get, though he will have to find the real Optimus after he's finished with this pathetic fool. This stunt he's pulled is quite sneaky for Optimus' standards. But Megatron could see where he was coming from. Luring Megatron out to fight his fake would keep his Autobots safe without worrying himself at the consequences of meeting the weak copy in close combat. He had to be here somewhere, as he knew the location Silas and this copy were. Megatron already knew his reasoning, but it never hurt to rib Optimus about his a bit more Decepticon traits that he'd picked up from once being close with a gladiator.

"Why don't we find out, fleshling?"

Even if he hadn't known this wasn't Optimus already, the stance the other picked would have told him everything, as would the fact that he attacked first. They had locked themselves in an unconscious dance throughout the centuries, taking turns in who's leading with the first attack. The last time they faced off was Optimus' turn, which meant this time it should have been Megatron's. Even though it wasn't a conscious decision on their part, it repeated itself like a general law of dynamics. They never strayed from the pattern. The fact that this fake Optimus engaged first in servo-to-servo combat was also completely un-Optimus-like, as the Prime _always_ first engaged him in a firefight to discourage close combat, as it usually led to longer battles, higher risks, more casualties and more energon lost in the process. Though, he had to give it to the fleshlings. The strength behind the first blow was almost accurate. The position it was meant to be delivered to, though, was not.

Megatron laughed as he easily stopped the punch meant for his faceplates as a distraction while equally as easily sidestepping the real blow meant for his side. The fake may not have any thought behind its movements to give it away, but its optics still revealed its next move. The human had to see, after all, and given their primal technology, they couldn't make optics or optic sensors to match the range a true Cybertronian's can achieve. As such, the yellow optics had to move in order to select a target. To a warrior as seasoned as Megatron was, it was like reading an open book, as the humans would say. He could read the human's intentions before his little drone could even begin making its move.

Familiarity with fighting the inspiration behind this particular drone wasn't helping this _Silas_ any. After the long millennia of fighting with his dearest rival and the centuries before that of them being as close as brothers, Megatron knew every minute shift of Optimus' every nut and bolt and screw. To most of the universe, Optimus was as stoic as they come, especially if he engages his battlemask. In truth, he was very expressive, if only one knew where to look. Not only the optics gave him away. Megatron could see the direction his opponent might be going or on just what Optimus was focused on by tracking the movement of those ridiculously endearing audio finials of his. They were as telling as seeker wings or door-wings, particularly in Praxians. Unknowingly, the humans had managed to install these sub-processor reactions into their drone as well, only leaving Megatron with more advantages. He avoided several more blows with the ease of a dancer before growing tired. Without bothering to power up his Fusion Cannon or extend his blade, Megatron plunged his claws deep into metal plating when he saw an opening only he knew Optimus had on his left side. The drone spasmed, not in pain but as a reaction to many of its systems being cut off as Megatron's claws damaged the T-Cog and some very important cables and circuits. Yellow optics flickered as the drone tried to focus in on his face.

Megatron laughed, hoping the human can see every single one of his sharpened dentae. "You are a special kind of fool, flesh bag. I know the body of Optimus Prime better than his medic!" He twisted his servo in the fake's chassis, enjoying the sound of straining wires he was holding and crunching metal as he moved his hand around. If he went any deeper and a little upwards, he'll be able to puncture the fake's energon tanks. A lethal blow, even in a mindless drone. "I know best how to both bring him pain as well as pleasure. Perhaps you would have been a better challenge had you picked anyone else for your little experiment. It would have at least held an element of surprise! As it was, this was rather disappointing." He shoved his talons in deeper, expression becoming stoic. "I grow tired of you. Come now. Put up at least a _bit_ of a fight."

The left servo of the fake turned into a blaster and tried to fire him in the face, but Megatron just jerked his wrist and his opponent keeled over, using his other servo to crush the weapon beyond what self-repair systems could ever fix it from. He had to give it to the human that he was stubborn, as the right servo of the drone transformed into a blade and it was directed to cut into the seemingly less armored waist of the silver behemoth, but Megatron wasn't the Champion of the Pits if Kaon for nothing. He just finally thrust his servo as deep as it could go, puncturing the tanks and destroying part of the ventilation systems and the drone spasmed again, falling utterly still as yellow optics flickered on and off, on and off before completely fading as the drone was forced into shut down due to the lack of energon in its systems. Megatron grunted in disgust as he wrenched his servo free, pausing only to drag out the salvageable T-Cog out of the drone. Spare parts were always appreciated by medics. Knock Out might appreciate it. Not to mention that Megatron could blow this whole place up and as thus destroy the humans that had once experimented on the medic's partner. Keeping medics happy was always the best way to go, as the Arena had taught him, vorns ago.

But he had much better things to do than worry about fleshlings.

He had a Prime to hunt down.

00000

Optimus was honestly surprised when Megatron left after only a five minute, halfhearted search of the facility. He had expected a bit more of a fuss from the warlord because the lack of his should-have-been-opponent, especially after the glee Megatron had shown in telling Silas and MECH just how their copy fell short. Optimus tried not to be flattered and embarrassed by the things Megatron had said and tried to ignore the flabbergasted reactions his team and their human allies were having to some of the things the silver tyrant had revealed. Thankfully, Ratchet's rant at Megatron's claims that in some way insulted his medic pride were distracting them enough from asking questions that Optimus refused to answer. What had happened between Orion Pax and Megatronus was seriously none of their business. It had happened millions of years ago and it should really stay in the past.

Though, truth be told, nothing that has ever happened in his past tended to actually _stay_ there. He wonders briefly if this was his punishment for failing to stop Cybertron from going dark. But Primus loves his Prime and wouldn't spit on him out of spite.

Optimus knew damn well that the deity would do it for its own amusement. The connection between them provided by the Matrix had revealed that a long time ago, as it went both ways. Optimus had really doubted Primus knew what he was doing when he threw his vassal into situations as ridiculous as this one. He could not see how embarrassing him in front of his soldiers could help in bringing peace to their species or ending the war and eventually, perhaps, rehabilitating and re-inhabiting Cybertron to its full glory once more, only better for the lack of the caste system that had started this whole mess in the first place.

So deep was he in his thoughts that Optimus actually didn't hear the approach of heavy but surprisingly light pedesteps until he was whirled around and slammed against the rather sturdy wall of the building he had been hiding behind while watching his enemy dismantle his copy. He winced as his battle protocols roared to life and his servo started transforming into a blaster, but that servo was shoved upwards and the shot harmlessly aimed towards the sky while a heavy, familiar chassis pressed against his own, successfully trapping him against the building. He looked up, already knowing his captor and dreading the expression that might be on the silver tyrant's face.

He had expected anger, battle-lust, indignity. He had not expected the excited grin that adorned Megatron's faceplates as the slightly bigger mech leaned down to speak in his audials. "Why, Optimus! How very sneaky of you, to have me dispatch of your problems! So devious. Are you sure you don't have a bit of Decepticon in you?"

"What do you want, Megatron?" He asked, trying not to show just how unsettled he was to have both his arms now pinned above his helm. It was hard to repress a shiver as warm exvents tickled over his sensitive audio finials, but he would not give Megatron the satisfaction.

"Why did you do it?" The former gladiator asked, tilting his helm to look at the Prime better, apparently amused by the battlemask hiding his face. "What could you possibly have hoped to accomplish? I know this wasn't an assassination attempt, for not even Starscream would be stupid enough or desperate enough to rely on such a weak imitation to defeat me."

"You've said it best yourself, Megatron," Optimus admitted in a tone that on any other bot might have been sulking, but not on Optimus Prime. On Optimus Prime it was mildly annoyed at best. "You know how best to cause my body pain."

Megatron's grin took on an edge that Optimus had not seen since that night before they spoke in front of the Council. It made Optimus shift uneasily, suddenly acutely aware of his vulnerable position and just what the other mech could do to him. "If you were listening, then you know you are quoting only a part of my statement, dear Optimus. It's not like you to selectively quote someone. I do believe my exact words were 'I know how to bring him both pain as well as _pleasure_'." Optimus couldn't hold back a shiver as Megatron revved his powerful flight engine and the vibrations of it traveled from the warlord's frame to his own. The Decepticon leader only grinned further at the reaction and tucked his helm so his lip plates were level with Optimus' exposed neck cables. "Perhaps I need to remind you of this?"

"Wha-? Megatron, don't you dare-Ah!" The gasp escaped him without his permission as Megatron started nibbling and sucking on a sensitive energon line and Optimus' battlemask slid aside involuntarily a moment later, as a skillful glossa joined in on the play of dermas and dentae. He wanted to knock that smug smirk off of the fragger's faceplates when he felt them against his neck, but before he could further contemplate that course of action, Megatron had already struck.

Optimus moaned into the unexpected lip-lock out of both surprise and pleasure it caused him. He barely had the presence of mind to completely cut the link to base - he'd cut the visual feed the second Megatron had pinned him to the wall, for he had known something like this could occur - with barely a message saying he was busy dealing with Megatron without specifying in just what _way_ said dealing was taking place and ordering them to stay at base and _not_ repeat the stunt they had pulled during Unicron's awakening. Megatron remained oblivious to the split attention of his companion and just continued his ministrations, wicked sharp claws delving beneath plating to tease at sensitive wires and coping a feel even as he still restrained Optimus with his other servo.

Optimus knew he should probably push the other away, make him desist, but the memories so recently stirred when he had dispersed the power of the Matrix into Unicron's spark had him hesitating. It had awoken a longing he had thought long since managed and buried and had unearthed a hope to finally change Megatron's mind and attitude about the pointlessly ongoing war. In truth, he wished nothing more than to create a scenario in which the war ended not in either of their deaths, but in a reunion. Optimus knew he must mean something to the former gladiator if Megatron had stilled his servo from killing him, whatever the ulterior motives could have been. Decoding the Iaconian database was something he could have had Soundwave do, even if it would have taken longer. He had no real practical reason in keeping Orion Pax online when he had had a perfect chance to offline Optimus Prime in his vulnerable state.

It let Optimus hope and it was this hope that prevented him from pushing Megatron away. It felt rather bittersweet, all things considered, but he knew this might very well be his last chance to hold Megatron like this, his last chance to change his mind and urge him to agree to peace. He let his field pulse with acceptance and a long since buried emotion that had no place being attached to his enemy and he felt Megatron still, his vents hitching. And then his servos were released and those wicked sharp claws were holding him close, guiding his thighs to wrap around a silver waist as the other hoisted him up, longing and that same feeling echoed in his once brother's field back to him, the kiss growing frantic.

Optimus couldn't smother his smile against those sharp dentae, spark whirling with an unbearable excitement and the Matrix contentedly warm in his chassis, sensing a fate/world/life-altering change taking place and wholeheartedly agreeing with it. Optimus shushed its encouragement so he can focus on the mech that was trying to devour him whole while holding him almost too tight in the strong embrace as he caressed spiked shoulder guards and the strong chassis holding him up. He was neither a small nor a light bot. The display of strength sent a shot of charge through his body and his field and Megatron growled in approval, one servo traveling up a shapely leg to rub at a panel that hadn't been touched by anyone in far too long.

Optimus gave a loud gasp as his helm clanked against the wall behind him, utterly content to let Megatton demonstrate this knowledge and ability of his that he so boasted about.

It's not as though it's not reciprocated.

Know thy enemy and all.


	2. Chapter 2

**Know Thy Enemy**

**Summary: I just rewatched S1 and part of S2 of TFP and wondered how else episode Nemesis Prime could have gone if a certain warlord got involved. Two different ways it could have gone. Mech on mech slash.**

Optimus grunted as his copy slammed into him, trying to send him to the ground - or rather the roof they were fighting on in the abandoned industrial complex - so as to dispatch of him once and for all, but Optimus was having none of that. He had not survived millions of years of war against the Decepticons and thousands of battles against their ferocious leader just to be felled by an impersonator. Call it some sort of injured pride or the vanity even a Prime has in certain amounts, but Optimus refused to be defeated by a cheap knockoff. He grabbed at the kibble available to him and the remote-control drone went down with him, the two already in the midst of a wrestling match when an all too familiar chuckle reached Optimus' audials, making his finials perk up. He cursed his single-minded focus on his counterpart, for it would seem he had not registered the approach of a _much_ greater threat than MECH could _ever_ hope to pose.

Said threat had somehow managed to sneak up on the wrestling pair of semi-trucks, who had now stopped said wrestling to both look up at the huge, spiky, silver war machine watching them with wicked, amused red optics, taking in the sight of two Optimus Primes pressed so close together, the far more innocent blue optics wide with dread while the yellow ones were emotionless in their lack of life or spark. That didn't make his frame any less _Optimus_, even though it was a cheap knockoff. It was a sight to behold, a fantasy and Megatron was very glad that every Cybertronian can take snapshots and store them in their memory files, for this is not something to miss out on or forget. It was too enticing a sight to let such a memory fade.

"Well, well, well! Imagine my surprise when I was taking a casual flight to get away from my imbecile soldiers when I picked up your signal out in the open. This was not what I had expected to see," the warlord chuckled as he stalked closer to the intertwined pair, red optics drinking in as much of the sight as he possibly could without circling them like a predator would its pray. "Optimus, who is your friend? I never thought you to be one for something so ... egotistical." A wide grin settled on his scarred dentae when he noticed how the imposter was placed between Optimus' thighs, wicked ideas rushing through his processor. "Mind if I join in?"

"You will have your turn later, machine, after I am through with him," Silas said through the drone's vocalizer and Optimus turned incredulous blue optics on his opponent. Did he even realize how suggestive that sounded? Probably not, as humans who knew of their presence on Earth besides the kids, Agent Fowler and Mrs Darby didn't even know that Cybertronians weren't really all that different from them in _many_ aspects, quite possibly due to the planet itself and its more ... sinister, let's say, nature than most would think due to how and around what it was formed (he'd be more surprised if they _weren't_ so similar, given that humans were technically Unicron's progeny, in a sense; a far off, organic cousin of the Cybertronians. Who would have thought?) and what exactly was in its core. Silas probably had no idea that 'robots' can copulate. He wouldn't see the double meaning. But Megatron was certainly in the mood for it and Optimus suddenly just wanted the ground to swallow him whole so he can escape what promised to be a disaster and incredibly embarrassing. Maybe if he had actually been on the ground, Unicorn would have indulged him, but he was on this accursed roof, all splayed out for Megatron's leisure to ogle at.

Megatron's grin suddenly vanished, replaced by a cold look the Prime recognized from the times he had come to watch Megatronus' fights in the arena and someone tried to hold back his little Iaconian archivist from getting to him after said fights were over and battlelust still raged through his systems. Optimus cursed internally but just sent a glare at Megatron on the outside. "Megatron, I am currently occupied. We can deal with whatever you want later."

He winced when he saw the fury and possessiveness in the former gladiator's optics and cursed his own processor-to-mouth filter when he realized the double meaning his _own_ words could hold. And even if they didn't, Megatron had never been one to be ignored, _especially _not by _certain _red and blue mechs. He had never been one to allow Optimus Prime to fight anyone else but himself. In the millions of years that their war had lasted, never once had Megatorn let another lock blades with Optimus Prime. He wasn't one to share what was _his_, even if that possessive noun only figuratively described said possession, as Optimus was _not_ owned by _anyone_. He just happened to be Megatron's enemy. And, once upon a time, something else.

Optimus wasn't even surprised when Silas' drone was yanked off of him with enough force to rip apart an Insecticon and he watched in fascinated horror as Megatron flung his doppelganger off of the roof as though he weighted nothing. Megatron had done much the same to him a few times, over the course of their war. Even after the Matrix had upgraded his frame, Optimus often felt as though he weighted nothing to the silver Decepticon. Not a comforting thought when he was surrounded by enemies. He found he couldn't remove his optics from the former gladiator as Megatron stormed after his dobbleganger, blade out and deflecting the blaster fire that 'Nemesis Prime', as Miko dubbed him, shot his way with a scary ease. Even the few shots that landed did little more than scrap a few surface paint nanites and that was hardly visible against Megatron's protoform. Silas abandoned the drone's guns and instead fell into a fighting stance with both blades drawn out. He charged at Megatron, not as foolishly as he himself had when he had lost all memories of being Prime but foolishly enough to think he could land a blow to the Champion of Kaon.

Optimus was still too stunned by the fight going on to move or even think about leaving while he had a chance or maybe finding the base of operations. He felt like that same little archivist, watching his first gladiatorial match, utterly transfixed by the show of strength and power and skill of a true gladiator. He wondered if his fights with Megatron used to be as awe-inspiring at the beginning of the war, when it was a novelty that any one mech can stand up to the Lord of the Decepticons. Even though Optimus recognized Silas' skills and the drone's lack of pain didn't give them the 'edge' Silas had bragged about in their fight - no matter the fighting style, Megatron had had millions of years to learn every single one of Optimus' weaknesses and sensitive spots. A new fighting style won't throw him off - it was still captivating. It was a fight of two titans, though the drone was by no means evenly matched with Megatron. It may have all of the Prime's strengths and abilities, but it lacked the one thing that truly allowed Optimus to stand against Megatron again and again and again and that was the knowledge of _Megatron's_ body to equal Megatron's knowledge of his. Silas was fighting a completely new opponent while Megatron was trouncing a _much_ weaker version of an opponent he was more than used to fighting.

Even grappling or fist to fist didn't help the drone. Silas didn't know what to aim for, what to grab to have a decent hold or to gain the proper leverage to potentially overbalance the Decepticon. Megatron just laughed at his failed attempts and Optimus knew he was only toying with the human.

"Optimus, what is going on out there!?" Ratchet's voice blared from his comm link and the Prime winced at the volume. It cut through the sounds of the fight like a knife through butter and made him snap out of his little staring session. He had not even realized he had forgotten the reason why he was here or about MECH.

"It would seem I have gotten some unexpected help, old friend. From a _very_ unexpected source."

"What? From who? Is Wheeljack back?" The medic asked, perplexed and Optimus transmitted to him what he was seeing, practically _hearing_ Ratchet's jaw drop when he saw Megatron fighting the fake. "What is _Megatron_ doing there and why the _Pit_ would he help you?"

"I am still uncertain, but it would seem he is keeping Silas and MECH plenty busy. If Agent Fowler wishes to carry out the arrest, I advise he do so now, as I doubt we'll get a better chance." Putting an end to mech was their top priority. They were a danger to humans and Cybertronians alike and needed to be taken care of. The sooner, the better.

"Then it's a good thing we already triangulated the signal from the remote control device they're using to move Nemesis Prime. It's actually nor far from your current position."

"Then I will be on standby should Agent Fowler need me. I am reluctant to leave Megatron unsupervised otherwise." That and it had been a long time ago that he had last seen Megatron in his element without being on the receiving end or having to pretend that he was surprised/horrified/disgusted by the display. He had seen one too many Pit matches to be innocent of the carnage that such fights could produce. There was a time when he had been utterly fascinated by gladiators and their unique culture, so separate from even Kaon's less than savory ways. Gladiators used to be viewed as _heroes_ to the lower caste mechs, even though they were nothing but barbarians to any middle or upper caste bots. Orion Pax had quite possibly been the only exception.

Ratchet gave him some sort of affirmative that flew right over his helm as he watched Megatron get bored of playing with his double and unsheathed his blade right into the copy's throat tubing. He couldn't even wince at the image of his own throat sliced as energon poured out of the severed cables, optics wide and focused on the silver mech as he stepped away from the deactivated and utterly useless robot, letting it fall down in an undignified heap at his pedes with a victorious snarl. Optimus almost expected him to roar "I still function!" like he used to after every fight in order to rail up the crowd. Not that they had ever needed any additional encouragement to chant his name. Optimus swore his spark was spinning with the long lost echoes of the cheering audience and the applause of thousands of mech as though they were still in Kaon, still in that arena where everything had started. It was almost as though they had gone back in time. His elevated position on the roof only strengthened that silly feeling as it was almost the same perspective he had had of all but Megatronus' first match that he'd watched in person. It was so disorienting that he almost applauded the show.

But then the optics that trained their sharp gaze on him weren't blue but as red as his own paint and Optimus was snapped out of the illusion created by the display. He scrambled away from the edge of the human construction, intent on escaping before a fight might break out - he felt too off kilter to safely engage with his once brother - but before he could get back to his pedes, Megatron had already climbed up and was stalking towards him like a predator, optics burning in a way that _really_ left the Prime feeling like that small archivist again, freezing for only a klik in his escape attempt. The tyrant used this slight hesitation to his advantage and pounced, catching Optimus before the other could evade him in some way. The grappled for a few minutes, rolling around the roof and trying to get the upper hand, a battle far more on equal ground than the drone could have managed, until Megatron gave a snarl and managed to pin Optimus underneath him, the Prime still struggling to make a break for it. But Megatron slammed him against the rooftop, his helm smacking painfully against the hard metal, making him dizzy enough to stop struggling for a few seconds. Megatron capitalized the opportunity and better secured his hold on Optimus, even managing to pin both of his servos over his helm with one of his own and settling most of his weight on the pinned truck so he couldn't trash around too much in search of freedom.

Optimus tried struggling again but fell utterly still when sharp dentae nipped at his exposed throat tubbing, cursing that he had no protective armor there and that his neck was so sensitive as a result. It was both dangerous and arousing and Megatron _knew_ it, the fragger, especially if the grin he felt developing against his neck cables was anything to go by. The Prime scowled beneath his battlemask, thankful for its presence. Though Megatron didn't seem to agree, judging by how impatiently he was tapping a sharp claw against it. As if Optimus was going to retract it for him. As if that was going to happen after how he had treated him when he had had amnesia. Optimus didn't remember everything, but the fresh feeling of despair and betrayal he had woken up to upon the Matrix being brought back online was one he had only felt once before. His Autobots had completed the picture by telling him what they knew about what had happened.

There might have once been a time when he would have welcomed this, but not after he learned just how little regard Megatron held for either Optimus Prime _or_ Orion Pax. "Megatron, release me at once."

"Come now, Optimus. Is that how you greet a victorious friend after a death match?" He pulled back to look at the slightly smaller mech beneath him, his mind obviously having gone down much the same path as Optimus' has. He would be lying if he said he didn't miss this long forgotten dynamic. He should hate it, that even after all these years this bot had this exact same effect on him as he had all the way back then, but he strangely found great comfort in it. It was ... nice, knowing some things never changed. The brief return of Orion Pax had affected him more than he had originally thought, but the return of Optimus Prime after three weeks of staring at a bot who might as well be a stranger behind familiar optics now had been a balm to a wound he had not even realized was there until it stopped stinging. For all that he and Orion had been close, there was a different sort of intimacy between him and Optimus. There had once been a time when he cursed the Matrix for reformatting his little archivist into his greatest enemy, but he had never thought he'd feel ... _lost_ without Optimus there. He had crossed countless galaxies in his pursuit of the Prime and to have him gone ...

Once, he had loved Orion Pax more than he had ever been ready to admit to even himself, let alone the archivist in question. Orion becoming Optimus had been the greatest betrayal he could think of and he had hated the mechanism that now occupied Orion's modified body. Now ... Now he found himself dreading the day a repeat of the amnesia incident happening, dreading and fearing the day his oldest rival might forget him once more. He was no more Megatronus than Optimus was Orion. He had no place in a world Optimus did not exist in. He didn't know what he'd do if Optimus were to offline before him. He had been very close to this realization back when the yellow Autobot scout had been bargaining for the cure for the Cybonic Plague but he hadn't been ready to acknowledge it. For so long, he had thought that snuffing Optimus' spark might bring him the greatest pleasure, right up until the moment he felt relief when the mech had caught his blade and told him to 'be gone'.

If this was continues, then it is more than likely that there will come a day when he feels like the world is empty for there would be no more Optimus in it. Watching the mech bellow him now ... It had Megatron questioning why they kept fighting. Cybertron has been dark for eons, by his fault, no less. Their species was scattered across the stars, scrambling for scraps to survive. There will eventually come a day when they have no more energon to sustain them, if they don't bring the Core of Cybertron back online and Megatron knew only a Prime can do that. They had a mutual enemy on this planet that had just tried to murder Optimus and may or may not have succeeded had Megatron not been around. Don't get him wrong, Optimus was a stellar warrior, but he didn't know how to utilize his own weaknesses against himself. He knew what they were and how he would defend them, but he had never tried to use them. The human controlling the drone didn't have that problem vice versa.

"What do you want, Megatron?" Optimus asked when the mech above him fell into a strange, thoughtful silence, his EM field drawn in far too tight to his protoform even for Optimus, who was in direct contact with a lot of his plating, to decipher what had the other so still.

"A ceasefire," he replied and felt indignant when he saw the incredulous look Optimus shot him. "Don't look at me like that, even I can grow weary of war."

"Judging by the state of my dobbleganger," Optimus drawled in a dry voice. "I failed to see this weariness that you speak of." When Megatron didn't reply, Optimus cocked his helm to the side, realizing Megatron was dead serious about this. "And how long do you propose for this ceasefire to last? When will you turn around and point your blade at me once more?"

"Preferably, never, but we shall see." He grinned at the stupefied expression on Optimus' face, greatly enjoying that he still had the ability to leave the Prime off kilter. It was rather hard and not just because Optimus kept his emotions in check rather well, especially with his battlemask on. They have known each other far longer than the humans recorded their history. Surprises are hard to come by when you think you've seen everything.

And yet Optimus surprised him by revealing his faceplates by retracting his battlemask, showing his uncertainty and almost unrestrained hope as he peered up at the warlord. "Why? What changed your mind? Why did you even help me? I thought you _wanted_ me dead."

Megatron scowled darkly. Why did _everyone_ seem to assume he'd be the happiest he could ever be if Optimus' spark goes out? Yes, he often yelled it across the battlefield that it was the day he'd do it himself, but that didn't mean he'd genuinely be _happy_ afterwards. He had suspected that outcome long before Optimus disappeared behind Orion's naivety and innocence. Perhaps it is what had stayed his hand so many times. He knew he was only alive because Optimus himself had never wanted to kill him, so they stayed evenly matched in pulling their punches against each other. He thought Optimus would know this, would know _him_ well enough to realize it. But then it occurred to him that Optimus _used_ to know this - why _else_ would he be so willing to trust Megatron against a threat like _Unicron_ \- but had probably started doubting it after the same event that had forced Megatron to admit his greatest, most well protected fear because of _Megatron's_ actions.

Well, he'll just have to set him straight and point out his foolishness.

"One, if I _wanted_ you dead, it would have to be by _my_ hand and no one else's. The fact you got the cure for the Cybonic Plauge should have driven that fact through your thick processor. I would not allow any other to do it and disgrace a warrior such as yourself, my only equal in every regard." _That_ already seemed to be surprising enough for the Prime, but ooh, Megatron was just getting started. "Two, the _why_ should be rather obvious. We are on the brink of extinction and it is time we stop contributing to that ourselves. We have fought far longer than it was needed. Surely all those functionists and caste system supporters have died by now. I rather doubt even the most loyal of Autobots would let such mechs hog all the precious energon all for themselves when millions of soldiers who need it _far_ more than them are starving. And _three_, what changed my mind, what could _always_ change my mind - most often for the better, was _you_."

Optimus was stunned by now, utterly and completely stunned. He didn't know what to say. He was surprised he could even whisper the other mech's name, not sure what he meant by it, if anything. Not sure if there was any other words to follow that one that stirred so many different emotions all the time.

Thankfully, he didn't have to say more, as Megatron wasn't finished yet. Though him touching their forehelms together was almost as shocking as the words that followed the gesture. "I nearly lost you, Optimus. To Unicron, to amnesia. Yes, I miss Orion Pax from time to time, but I have come to realize I could _never_ lose you. And the continuation of this war is exactly what might bring about that outcome. You are far too self-sacrificing, honorable, selfless and humble to let anyone else end it if you are given an opportunity. It took seeing Orion in your optics for me to realize how much emptier the world would be for me if _you_ ceased existing. He may have been my friend and my lover, once upon a time, but we all know the sayings of 'Keep your friends close and your enemies closer' and 'Know thy enemy.' I _know_ you, Optimus, in a way I never knew anyone else. I only just recently realized I couldn't stand to lose that."

And here Optimus thought Megatron would prefer Orion back instead of himself. Tonight was certainly an evening of surprises. The Prime searched those red optics for deceit very carefully, even reaching out to the Matrix for assistance, but all he found was truth and honesty. Relief flooded his field and happiness poured over him like warm oil. He suddenly felt eons younger. A chance. A chance to end the war without having to watch the one so dear to his spark offline. It was like he was weightless, floating. They could end this, all this death and suffering, _tonight_. And it had been Megatron who suggested it. That thought sent a shot of warm affection through his spark and Optimus followed the impulse to nuzzle his forehelm against the one resting against his. Megatron's field flashed with surprise before, too, being overwhelmed by happiness and relief.

It won't be easy. There was a lot of work to be done. Their troops probably won't take the news so well ... Or perhaps they will? Optimus couldn't find it in himself to care at that moment. He was perfectly content to nuzzle up against his (former) enemy and dream of peace.

At least until Agent Fowler and his fellow humans arrive to arrest Silas and MECH. Then they'll have to make themselves scarce so as not to create more problems than was necessary.

But for now he just enjoyed snuggled with Megatron on top of a human construction underneath the full moon. Call him a sap, but he thought it all rather fitting as to be their end as enemies.

Maybe they can get to know each other now as something else, finally.

**THE END**


End file.
